1. Field of the Invention
This invention is related to a method of managing external storage devices. In particular, the present invention is directed to a method of enabling access to encrypted data in external storage devices from one platform storage system to another platform storage system.
2. Description of the Related Art
Recent computer storage systems have a function called “external connection” which connects one storage system to other storage systems. The storage system discovers disk volumes in the external storage systems and exports them to host computers via its communication ports as if they are internal disk volumes in the storage system. If the storage system has advanced functions, for example, volume mirroring, a large capacity of cache memory, various types of host-connectivity, etc., it can provide these functions to external storage systems which do not have such functions. An example of a storage system having external storage systems is disclosed in U.S. Pat. No. 6,529,976 (entitled “Heterogeneous computer system, heterogeneous input output system and data back-up method for the systems”), the disclosure of which is hereby incorporated by reference. This patent discloses a storage system which has external connection functions and is called a “platform storage system”. Disk volumes in the platform storage system and external storage system are called “internal volumes” and “external volumes”, respectively.
In recent years, storage security has become an important concern for large enterprises and governmental organizations. Encryption is a common way to prevent illegal access to confidential data. Data written by host computers is encrypted by a storage controller before being stored in disk drives so that the data cannot be read by unauthorized users even if the disk drives are stolen. A storage appliance with such kind of encryption is disclosed in international publication WO 2002093314 (entitled “Encryption Based Security System for Network Storage”), the disclosure of which is hereby incorporated by reference. Some organizations are developing standards for storage security. For example, IEEE p1619 (Draft Proposal for Key Backup Format for Wide-block Encryption 1.04:00″, http://siswg.org/docs/KeyBackup-10-04-2004.pdf) defines standards for cryptographic algorithms and methods for encrypting data before the data is sent to storage devices.
When a platform storage system encrypts data to be stored in one or more external storage systems, the data can be read only if it is accessed via the platform storage system. However, that means if the existing platform storage system is replaced by a new platform storage system to update computer systems, the data cannot be accessed in the new system. In order to maintain accessibility, the data should be read via the old platform storage system, transferred to the new platform storage system, and encrypted by the new platform storage system. However, the process can be very time consuming when large capacity external storage systems are involved. This causes a long down time of the computer system which creates problems for businesses.